Undervaluing of mangroves in the Paris Climate Agreement

Almost two years ago, 147 Nations around the world agreed to reduce their carbon emissions in the Paris Agreement. In this historic agreement, nations committed to reduce fossil fuel consumption and deforestation. This was a crucial step forward in much needed international action on climate change.

As nations submitted their Intended National Determined Contributions -a document with goals for reducing emissions-, there was an important oversight: Mangroves were considered terrestrial forests.

Mangroves -not any kind of forest

As mangroves are flooded by the tide, they are more of a saltwater lake with trees growing from it than a forest. Mangroves differ from terrestrial forests in that they accumulate large amounts of carbon not in their trunks and leaves, but in their soil.

If we look back to deep time, during the Carboniferous period in the Palaeozoic Era, there were large swamps that were fossilized and formed huge coal deposits. This coal is the same rock we burn in power plants to power homes and industries, or burn in our BBQs to cook sausages on Sunday afternoon.

So mangroves are like a modern coal storing machines, similar to the swamps in the Carboniferous era.

In the Paris Agreement, mangroves in Mexico were measured as terrestrial forests and the large stocks of carbon in their soils were not included.

So what does this mean?

If you cut a forest that has 100 ton of carbon, it will emit to the atmosphere 367 ton of CO2, if you cut a mangrove forests with 1000 ton of carbon, it will emit, ten times more, or 3670 ton of CO2.

So if we don’t measure correctly how much carbon a forest has, we fail to estimate the emissions caused by their deforestation. In Mexico, mangrove carbon content is 31 times larger than what was reported in the Paris Agreement.

There was a good reason that mangroves were accounted as terrestrial forests in the Paris Agreement. The accounting for carbon has to be done in a standard way, and the national forestry commissions have to comply with these guidelines. Currently, they can’t justify the use of different methodologies for different kinds of forests.

However, the undervaluation of mangroves in Mexico means means we are undervaluing the importance of their protection.

Hopefully, the results in our recently published article in Conservation Letters, will help justify the inclusion of soils in future carbon accounts, such as Mexico’s carbon credit scheme.